Production Profile and Comparison Analysis of Main Toxin Components of Fusarium oxysporum f. sp. sesami Isolates with Different Pathogenicity Levels

Fusarium wilt is a critical fungus disease for sesame, which is induced by Fusarium oxysporum f. sp. sesami (FOS). In order to determine the toxin production profiles of the FOS isolates with different pathogenicity levels under various culture conditions, we evaluated the content variation of fusaric acid (FA) and 9, 10-dehydrofusaric acid (9, 10-DFA) produced by the 4 representative FOS isolates. Results indicated that the maximum amount of FA reached to 2848.66 μg/mL in Czapek medium, while 9, 10-DFA was mainly produced in Richard and Low-carbon Richard medium. The concentration of 9, 10-DFA on Richard culture medium varied from 0 μg/mL to 716.89 μg/mL. Of the 5 kinds of culture media, Czapek culture medium was the most conductive to produce FA. FA production was significantly affected by culture medium, culture time, and their interaction (***, P<0.001). The results suggest that there is no correlation between toxin production and pathogenicity level of FOS isolates. The findings give key information for the mechanism analysis of FOS- sesame interaction and pathogen control.

芝麻枯萎病是危害芝麻的重要真菌性病害，由尖孢镰孢菌芝麻专化型（Fusarium oxysporum f. sp. sesami，以下简称FOS）引发。为明确不同致病力水平的FOS菌株在不同培养条件下的毒素产生特征，本研究对4株代表性FOS菌株所产生的镰孢菌酸（fusaric acid，简称FA）与9,10-脱氢镰孢菌酸（9,10-dehydrofusaric acid，简称9,10-DFA）的含量变化进行了测定。结果表明，FA在查氏培养基（Czapek medium）中的最大产量可达2848.66 μg/mL，而9,10-DFA主要产生于理查德培养基（Richard medium）与低碳理查德培养基（Low-carbon Richard medium）。9,10-DFA在理查德培养基中的浓度范围为0~716.89 μg/mL。在5种供试培养基中，查氏培养基最利于FA的合成积累。FA的产量显著受培养基、培养时间及其交互作用的影响（***，P<0.001）。研究结果表明，FOS菌株的毒素产生能力与其致病力水平无显著相关性。本研究结果为解析FOS与芝麻的互作机制及该病原菌的防控提供了关键参考依据。